Unmanned aircraft typically have a propeller, engine and controller or other drive system that provides thrust to the unmanned aircraft, i.e. a force having a component in the direction of the aircraft's motion. The unmanned aircraft further may have various sensors, such as a speed sensor, altitude sensor, air pressure sensor, etc. whose outputs are used by the controller during a flight.
In case a sensor is no longer working or working erroneously, or in situations where the controller is defect, or in case an actuator driven by the controller is failing, the unmanned aircraft may end up in an uncontrollable situation wherein it continuously accelerates and finally crashes at high speed. In particular for unmanned aircraft that are used in civil neighbourhoods, such uncontrolled crash at high speed is unsafe and therefore unacceptable.
Unmanned aircraft have been developed with technology that brings the unmanned aircraft in a flight termination mode. Manual control is taken on the unmanned aircraft in order to have the unmanned aircraft carry out a safe, spiral-shaped landing. Such flight termination mode however assumes that the unmanned aircraft's speed is still controllable which is not the case when the aircraft is in an uncontrolled situation during a flight.
The flight of an unmanned aircraft that is no longer controllable may alternatively be terminated through use of a parachute. The use of parachutes however requires the presence of a weight and it involves risks: the parachute may not be rolled-up properly and therefore malfunction, the parachute may not completely open, etc.
It is an objective of the present invention to disclose an unmanned aircraft that overcomes the above mentioned problems. More particularly, it is an objective of the present invention to disclose a propeller-driven unmanned aircraft that is able to terminate a flight in a safe, controlled manner when the unmanned aircraft is in an uncontrolled situation wherein for instance its speed is increasing as a result of failing sensors or components, such that the unmanned aircraft no longer crashes at high speed in an uncontrolled manner.